In information recording media such as magnetooptical recording discs comprising a substrate and thereon a recording layer and a metallic layer and capable of rewriting information, it is to be desired that the dependence of the recording power on linear velocity is made small so that the recording power for recording information in said media does not largely vary with the inner peripheral and outer peripheral portions of the medium.
Usually, in the information recording medium such as the magnetooptical recording disc, a metallic layer is formed, in addition to a magnetooptical recording layer, on a substrate. The metallic layers which have been used so far in the information recording media of the type such as magnetooptical recording discs are composed of nickel alloys, aluminum metal or aluminum alloys containing 0.1-10% by weight of titanium. However, the metallic layers composed of aluminum metal or aluminum-titanium alloys had such a disadvantage that they are poor in corrosion resistance and cannot withstand a long term-service.
The metallic layers composed of nickel alloys had also such a serious disadvantage that the recording power required at the time of writing information in the information recording medium largely varies with the inner peripheral and outer peripheral portions of said medium, and thus the dependence of the recording power on linear velocity is still large.
With the view of developing information recording media which are excellent in corrosion resistance or longterm stability and which are small in linear dependence of the recording power on linear velocity, the present inventors prosecuted extensive researches to find that the information recording media having a metallic layer composed of an aluminum alloy containing at least hafnium are excellent in corrosion resistance and small in dependence of the recording power on linear velocity. Thus, the present invention has been accomplished.